Dashpot



Jan. 7, 1964 T. F. CRAMER 3,116,917

DASHPOT Filed Sept. 19, 1960 F-IGJ.

f I0 I 4 54;

2,50 28- so FIGZ. 34; 2* 4-56 72 f a 4 76 l 42 k\\\\ 1 s 40 48 INVENTOR.

6 THOMAS F. CRAMER ATTOR EYS United States Patent 3,116,917 DASHPOT Thomas F. Cramer, Stratford, Ontario, Canada, assignor to Holley Carburetor Company, Warren, Mich, a corporation of Michigan Filed Sept. 19, 1960, Ser. No. 56,741 6 Claims. (Ql. 2671) The invention relates to dashpots and refers more specifically to a dashpot including a reciprocal piston which dashpot slowly retards movement of the piston in one direction and permits rapid return of the piston in a second direction.

Dashpots have in the past had not only a slow retarding action but also a slow returning action. It is desirable in many installations and in particular in the control of throttle mechanisms that the returning action of the dashpot be quick while the retarding action remains slow to prevent the stalling of the internal combustion engine which the throttle controls when the throttle is suddenly released.

Although the above characteristics are to some degree obtainable by the use of constructions presently known, there does arise a problem of variations in characteristics as between any two dashpots. This is caused usually by the inherent design of the dashpot and the necessary tolerances in the manufacturing operations.

It is therefore an object of the present invention to provide a dashpot construction having a slow retarding action and a quick returning action and which is capable of being calibrated so as to produce uniformity of characteristics as between any two dashpots.

Another object is to provide a dashpot comprising a cylinder, 2. piston reciprocal Within the cylinder, and means for retarding the movement of the piston in one direction and aiding the movement of the piston in the opposite direction.

Another object is to provide a dashpot as set forth above wherein the piston includes a restricted passage extending axially therethrough and a second larger passage also extending axially therethrough and having a check valve at one end thereof.

Another object is to provide a dashpot as set forth above wherein a relatively strong spring is provided urging the piston toward one end of the cylinder and a relatively Weak spring is provided urging the valve portion of the check valve which is secured to a piston rod away from the valve seat.

Another object is to provide a dashpot as set forth above in combination with the throttle valve of an internal combustion engine whereby movement of the throttle valve in one direction is retarded and a quick return of the throttle valve in the opposite direction is permitted.

Another object is to provide a dashpot having a slow retarding action and a quick returning action which is simple in construction, economical to manufacture and efficient in use.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a diagrammatic representation of a carburetor secured to the intake manifold of an internal 3,116,917 Patented Jan. 7, 1964 ice combustion engine and having a throttle valve and a dashpot constructed according to the invention in combination therewith.

FIGURE 2 is a longitudinal cross section of the dashpot illustrated in FIGURE 1 taken on the line 22 in FIG- URE 1.

With particular reference to the figures a specific embodiment of the invention will now be disclosed.

In FIGURE 1 there is illustrated a throttle operating mechanism 12 operable between the intake manifold 14 and the carburetor 16 of an internal combustion engine (not shown) to control the fuel supply of the engine. In accordance with the invention a dashpot 1d constructed to have a slow retarding action and a quick returning action is provided in combination with throttle operating mechanism 12 to retard the closing of the throttle mechanism '12 to prevent stalling of the internal combustion engine when the throttle is suddenly released.

More specifically the throttle mechanism 12 comprises the throttle arm 18, throttle linkage plate 20, throttle shaft 22 and throttle valve 24. Throttle valve 24 is rotated in a clockwise direction on movement of the throttle arm 18 to the right as shown in FIGURE 1. Throttle arm 18 is spring loaded to return the throttle valve 24 to a closed position in the usual manner.

The dashpot 10 of the invention is provided to retard the closing of the throttle valve 24 as the throttle valve approaches an idle position on sudden release of the throttle arm 18 and to permit rapid opening of the throttle valve. Dashpot 10 comprises a cylinder 26, a piston 28 reciprocal within the cylinder, and means including the valve 30, spring 32 and passage 34 for allowing rapid movement of the piston 28 within the cylinder 26 in one direction and retarding movement of the piston within the cylinder in the opposite direction.

The cylinder 26, as shown best in FIGURE 2, is closed at one end by end wall 36 and is adapted to be secured to the carburetor or manifold of an internal combustion engine by convenient means, such as bracket 38, as shown in FIGURE 1. The other end of cylinder 26 is closed by means of cover 40 having axially extending peripheral annular flange 42 and opening 44 for rod 46 as shown. Gasket 48 is provided between cover 40 and cylinder 26.

Piston 28 includes the piston body 50, seal 52 and plate 54 which may be secured together by convenient means to permit reciprocation of the piston within the cylinder while preventing air from passing from one end of the cylinder to the other around the radially outer surface of the piston 28.

The piston body 5t is provided with a radially inwardly offset end portion 56 and a passage 34- extending therethrough whereby air is permitted to flow from one end of the cylinder to the other on reciprocation of the piston within the cylinder. The rate of air flow between the ends of the cylinder through passage 34 on reciprocation of the piston is controlled by means of a restric tion 58 within passage 34.

A second passage 69 extends axally through the piston body 59 as shown. Valve structure 30 is provided at one end of the passage 60 and is operable to prevent transfer of air through passage 60 from chamber 62 at one end of the cylinder to chamber 64 at the other end of the cylinder on movement of piston 28 toward wall 36 by rod 46 while it permits transfer of air through 3 passage 60 in the opposite direction on movement of piston 28 toward cover 4%) byspring 32. Thus rapid movement of the piston toward the cover 49 is possible while movement of the piston 28 toward the end wall as of the cylinder is retarded.

Valve structure 39 comprises the rod 46 extending through opening 44 in cover 49, plate 66 secured to the rod 46 on one side and to the valve 68 at the other side and spring 70 within the axial recess '72 in piston 28. Valve 68 is seated on valve seat 74 Within the recess '76 in piston 28 on axially upward movement of the rod 46, as shown in FIGURE 2.

The piston 28 is biased into the position shown in FIGURE 2 by means of the spring 32 when the throttle valve 24 is opened. Spring 32 is stronger than spring 70 so that on upward movement of the rod as the valve 68 is first seated on seat 74 to close passage 69 before movement of the piston 28 toward the end wall 36 of cylinder'26 starts as the throttle valve 2% is closed, as shown in FIGURE 1.

Thus in operation, as the throttle arm 18 is released resilient means (not shown) biases the throttle arm 13 to the left in FIGURE 1 to rotate the throttle valve 24 into the closed position shown, as the throttle valve 24 approaches an idle position the tab '78 on the throttle linkage plate 20 is caused to move the rod $3 of the dashpot 10 which has been in the position shown in FIGURE 2, in an upward direction to close the passage 64) as previously indicated by the seating of valve 68 on seat 74. On further counter-clockwise rotation of the linkage plate 16 the piston 28 is forced upwardly within cylinder 26 against the opposition ofspring 3:2.

The movement of the piston 23 toward end wall 36 of cylinder 26 is retarded by the air trapped within chamber 62 of cylinder as. The air trapped within chamber 62 is permitted to bleed into chamber 64 through the restricted passage 34. Thus, the amount of retardation of the piston movement and throttle valve can be controlled by the restriction 58.

When the throttle valve 24 is again opened the tab 78 moves out of contact with the rod 46 and the spring 70 unseats the valve 68 from seat 74 since upward pressure is no longer applied to the valve 68 through rod 46. Theair in chamber 64 is thenpermitted to pass freely back into chamber 62 through passage as as the piston 59 is moved toward the cover 40 under the influence of the relatively strong spring 32.

Thus it can be seen that in accordance with the invention there is provided a dashpot construction which retards movement of a piston associated therewith in only one direction. The dashpot of the invention is therefore particularly useful in applications such as in the control of throttie valves where a slow retarding action and a quick returning action is desirable.

The drawings and the foregoing specification constitute a description of the improved dashpotin such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. A dashpot having a slow retarding action and a relatively quick returning action comprising a cylinder having flowable medium therein, a piston reciprocally mounted in said cylinder having an axially extending passage therethrough, resilient means located between said piston and cylinder urging said piston toward one end of said cylinder, a check valve in said passage including other resilient means located between said valve and said piston biasing said valve in an open direction, a reciprocal rod secured to said valve and operable on axial movement toward the other end of said cylinder to close said valve in opposition to other resilient means and move said piston toward said other end of said cylinder, said check valve and other resilient means providing substantially unrestricted flow of said medium through said passage from said one end of the cylinder to the other end thereof on movement of said piston toward said one end of the cylinder with the rod free to move outwardly of the housing, and means providing restricted flow of said medium from said other end of the cylinder to said one end thereof on movement of said piston toward said other end of the cylinder.

2. A dashpot having a slow retarding action and a relatively quick returning action comprising a cylinder having flowable medium therein, a piston reciprocally mounted in said cylinder having an axially extending passage therethrough, resilient means located between said piston and cylinder urging said piston toward one end of said cylinder, at check valve in said passage including other resilientmeans located between said valve and said piston biasing said valve in an open direction, a reciprocal rod secured to said valve and operable on axial movement toward the other end of said cylinder to close said valve in opposition to said other resilient means and move said piston toward said other end of said cylinder, said check valve and other resilient means providing substantially unrestricted flow of said medium through said passage from said one end of the cylinder to the other end thereof on movement of said piston toward said one end of the cylinder with the rod free to move outwardly of the housing, and a second passage through said cylinder having a controlling restriction therein providing restricted fiow of said medium from said other end of the cylinder to said one end thereof on movement of said piston toward said other end of the cylinder.

3. Structure as claimed in claim 2 wherein the first said resilient means is stronger than said other resilient means whereby said valve is closed before said piston is moved toward said other end of the cylinder on axial movement of said rod.

4. A dashpot including a cylindrical housing, a piston reciprocally mounted in the housing, a flowable medium within the housing, first resilient means located between said piston and housing biasing said piston toward one end of the cylindrical housing, a restricted passage extending axially through said piston for permitting ,restricted flowing of said medium from the other end of the housing to said one end of the housing on movement of the piston toward said other end of the housing, a second axial passage extending through said piston, a check valve carried by said piston in one end of said second passage thercthrough and second resilient means located between said valve and piston means biasing the check valve toward said one end of the housing into an open position and means connected to said check valve for closing said check valve in opposition to said second resilient means and for, moving the pistontoward said other end of the housing, said, check valve and second resilient means being operable to permit substantially unrestricted flowing of said medium from the one end of the housing to said other end of the housing on movement of the piston toward said one end of thehousing with the means for closing said check valve free to move toward the one end of the housing.

5. Structure as set forth in claim 4 wherein said first resilient means is stronger than said second resilient means so that said valve is closed before said piston is moved toward said other end of the housing.

6. A dashpot including a cylinder having closed ends, a piston reciprocally mounted in the cylinder, a flowable medium within the cylinder, first resilient means operably connected to said piston for biasing said piston toward one end of the cylinder, said piston including means for permitting restricted flow of said medium from the other end of the cylinder to said one end of the cylinder on movement of the piston toward said other end of the cylinder, a passage extending axially of said cylinder through said piston, a valve carried by said piston in said passage and second resilient means operably connected to said valve for biasing the valve toward one end of the cylinder into an open position and means connected to said valve for closing said valve in opposition to said second resilient means and for moving the piston toward said other end of the cylinder, said valve 5 and second resilient means being operabfte to permit substantially unrestricted flow of said medium from the one end of the cylinder to the other end of the cylinder on movement of the piston toward said one end of the cylinder with the means of closing said valve free to 10 move toward the one end of the cylinder.

References Qited in the file of this patent UNITED STATES PATENTS Sigel Dec. Tibbetts June Mercier et a1 Aug. Gillaspy Nov Olson et a1. Jan. Reppert et a1. Feb. 

1. A DASHPOT HAVING A SLOW RETARDING ACTION AND A RELATIVELY QUICK RETURING ACTION COMPRISING A CYLINDER HAVING FLOWABLE MEDIUM THEREIN, A PISTON RECIPROCALLY MOUNTED IN SAID CYLINDER HAVING AN AXIALLY EXTENDING PASSAGE THERETHROUGH, RESILIENT MEANS LOCATED BETWEEN SAID PISTON AND CYLINDER URGING SAID PISTON TOWARD ONE END OF SAID CYLINDER, A CHECK VALVE IN SAID PASSAGE INCLUDING OTHER RESILIENT MEANS LOCATED BETWEEN SAID VALVE AND SAID PISTON BIASING SAID VALVE IN AN OPEN DIRECTION, A RECIPROCAL ROD SECURED TO SAID VALVE AND OPERABLE ON AXIAL MOVEMENT TOWARD THE OTHER END OF SAID CYLINDER TO CLOSE SAID VALVE IN OPPOSITION TO SAID OTHER RESILIENT MEANS AND MOVE SAID PISTON TOWARD SAID OTHER END OF SAID CYLINDER, SAID CHECK VALVE AND OTHER RESILIENT MEANS PROVIDING SUBSTANTIALLY UNRESTRICTED FLOW OF SAID MEDIUM THROUGH SAID PASSAGE FROM SAID ONE END OF THE CYLINDER TO THE OTHER END THEREOF ON MOVEMENT OF SAID PISTON TOWARD SAID ONE END OF THE CYLINDER WITH THE ROD FREE TO MOVE OUTWARDLY OF THE HOUSING, AND MEANS PROVIDING RESTRICTED FLOW OF SAID MEDIUM FROM SAID OTHER END OF THE CYLINDER TO SAID ONE END THEREOF ON MOVEMENT OF SAID PISTON TOWARD SAID OTHER END OF THE CYLINDER. 